Improving the thermal stability and n-butanol oxidation activity of Ag-TiO2 catalysts by controlling the catalyst architecture and reaction conditions

We demonstrate a novel methodology of encapsulating and dispersing Ag nanoparticles in a reducible, mesoporous TiO2 nanosphere to enhance thermal stability and catalytic activity for VOC oxidation. Through comparisons with surface-impregnated Ag-TiO2, which suffer from significant sintering and deactivation after aging at 550 degrees C, we show that encapsulation helps maintain a uniform Ag particle distribution (2-5 nm) and promotes metal-support interactions by maximizing interfacial sites, thereby improving activity and stability. In addition, we discover that subjecting the encapsulated catalyst to a post-synthesis solvothermal treatment step anchors the active metal more strongly to the support, which helps maintain superior activity under repeated aging cycles. Finally, recognizing that industrial flue gas streams inevitably contain water vapor we examine a constructive method of deliberately exposing the catalyst's surface to water vapor before beginning the reaction. This simple method enhances the rate of VOC oxidation up to six-fold at temperatures as low as 40 degrees C.